1. Field of the Invention
The invention relates generally to suspended grid ceiling systems which are used in supporting ceiling panels. More specifically, this invention covers an improved connection for assembling such grid systems.
2. Description of the Prior Art
Ceiling grid systems customarily comprise a plurality of parallel main runners and a plurality of parallel cross runners perpendicularly intersecting the main runners. The cross runners normally have locking connectors on each end insertable through openings in the main runners. Many of the early systems used locking connectors on the ends of the cross runners that were relatively easy to disassemble. However, these systems no longer meet many of the building codes. Building codes, to improve safety in seismic areas, have been revised to require ever higher locking tension requirements.
A new family of cross runner lock connections were designed to meet these high strength requirements as disclosed in U.S. Pat. Nos. 3,922,829; 4,108,563; 4,601,153 and 4,317,641. Their general construction entailed cross runners with like connector ends, each having a single detent and aperture. Although these connectors met the increased code requirements, these locks could not be disengaged without major distortion or destruction. This problem of trying to achieve high locking strength together with removability was addressed earlier, i.e., U.S. Pat. Nos. 4,621,474 and 4,648,230. Both of these lock designs have a removable sequence which is initiated by a lateral force. When lateral forces are applied to such cross tees, they can be withdrawn. This is a major flaw since a disengaging lateral force could be applied unintentionally when placing panels or light fixtures or by a seismic disturbance.